1. Field of the Invention
The present invention relates generally to methods of treating sugar liquors, syrups, juices, and related products, offering compositions of matter and processes incorporating the same.
2. Description of the Prior Art
The use of activated carbon to decolorize sugar solutions is a well-established technology (Cane Sugar Handbook, 12th Ed., pgs. 463-464). The traditional process incorporates either a granular activated carbon (GAC) or powder activated carbon (PAC). In the granular carbon process, the GAC is packed in a tower, and impure sugar flows through the packed towers. The effluent from the tower is thus more pure, due to the decolorization power of the GAC. To prevent pH drop of the sugar liquor, about 5% magnesite (MgO) can be mixed with the GAC (Cane Sugar Handbook, 12th Ed., pg. 463). In the powder carbon process, the carbon is traditionally used as either a batch-contact followed by filtration to retire the powder carbon, or the powder carbon can be used as a precoat on the filters (Cane Sugar Handbook, 12th Ed., pg 464). In the batch-contact PAC method, a filter aid (usually diatomaceous earth or perlite) is almost always used, at a ratio of approximately 1:1 in weight to the PAC dosage. The filter aid assists with the filtration of impurities in the sugar, as well as assists with the filtration of the powder carbon particles. Generally speaking, the PAC is not buffered with another material (unlike the typical ˜5% MgO buffering of the GAC.)
In the sugar production processes, it is generally desirable to avoid or at least minimize sucrose sugar losses due to inversion of the sucrose into glucose and fructose. Inversion of sucrose occurs under acidic conditions (pH less than 7.0). Some sources advocate maintaining pH of all liquors and syrups (throughout the sugar production process) to be kept over pH 7.0 to avoid/minimize inversion of the sucrose sugars (Cane Sugar Handbook, 12th Ed., pg. 634). Many activated carbons for use in sugar purification are acidic in nature; this is due to the well-known property of acidic activated carbons to possess a greater ability to decolorize sugar juices, liquors, and syrups. Without buffering (with a base such as MgO previously mentioned for use with GAC), there is a risk of inversion losses in the sugar solutions treated with acidic activated carbons.
In other sugar processes, it is desirable to remove certain ash constituents such as calcium and magnesium. Calcium and magnesium can be naturally occurring in the sugar solutions, or added as part of a clarification process; for example, the sugar refinery industry standard clarification methods of carbonatation and phosphatation both utilize lime (Ca(OH)2) addition to the sugar solutions. Other examples of introducing calcium or magnesium into the sugar purification process include adding lime or milk of magnesia (Mg(OH)2) to the juice extracted from cane or beet sugars. In any of these situations, the calcium and magnesium in the sugar can beneficially react to remove a variety of impurities, usually with a mechanism of forming insoluble precipitate complexes between the impurities and calcium and or magnesium. However in most cases there is always residual calcium and magnesium that remains unreacted; the unreacted calcium and magnesium can cause undesirable side effects such as the formation of scale on evaporators. Therefore it is desirable to find methods that reduce the amount of unreacted calcium and magnesium during the sugar purification process.
More recent processes for sugar liquor and syrup clarification include those exemplified by U.S. Pat. No. 5,281,279 to Gil et al. This patent describes a process for producing refined sugar from raw sugar juices. The process includes adding a flocculant for treating raw sugar juice, wherein the flocculant is selected from the group of lime, a source of phosphate ions, polyelectrolyte, and combinations thereof. The thus treated juice is concentrated by evaporation to form a syrup, with a subsequent treatment by flocculant, then filtered, and then decolorized and de-ashed using ion-exchange resin.
In U.S. Pat. No. 4,247,340, Cartier claims a process for purifying impure sugar solutions, including simultaneous decolorization and clarification, comprising contacting the impure sugar solutions with submicroscopic ion-exchange resin in the forms of approximately spherical beads, said ion-exchange resin having diameters from about 0.01 to 1.5 microns, followed by separation of this ion-exchange resin from the sugar solution. The ion-exchange resin particles may be separated in the form of a floc, wherein the floc may be formed either from impurities in the impure sugar solution, or by adding sufficient flocculating agent in the sugar solution to flocculate all of the resin particles.
Another example of more recently proposed sugar clarification includes that of U.S. Pat. No. 5,262,328 to Clarke et al, detailing a composition for the clarification of sugar bearing juices and related products. The composition comprises a dry, powdered admixture of aluminum chloride hydroxide, lime, and activated bentonite. The composition may also include a polymer flocculating agent, such as a polyacrylamide.